Pressure vessel



F. E. FREY PRESSURE VESSEL May 16, 1950 Filed NOV. 27, 1945 m WJ INVENTOR ATTORNEYS Patented May 16, 1950 PRESSURE VESSEL Frederick E. Frey, Bartlesville, kla., assignor to Phillips Petroleum Company, a corporation of Delaware Application November 27, 1945, Serial No. 631,148

21 Claims. (Cl. 220-3) This invention relates to vessels for containing fluid under pressure. In a, more specific aspect, it relates to containers suitable for storing and transporting liquefied petroleum gas, compressed fuel gas, uncondensible gas, and other materials which must be held under superatmospheric pressure at room temperatures when the desired quantity thereof is in the container.

In the prior art, pressure vessels have been constructed as a cylindrical steel body which has been Wound with steel wire in one or more layers. These prior art vessels take advantage of the high tensile strength of steel wire, and thereby make it possible to obtain greater resistance to internal pressure with a minimum weight of steel, considering both the steel of the cylindrical shell and the Wire wound thereon.

l have found that certain organic fibers, preferably those composed of long chain molecules which molecules are preferably relatively highly oriented to give strength, exhibit very high tensile strength when compared with the tensile strength of steel wire if the weight of the fibers and the wire is taken into consideration. An outstanding example of these oriented bers is Nylonf which is a trade-name for a polyamide produced by condensing adpic acid and hexamethylenediamine. Other suitable iibers are Rayon which is a trade-name for a regenerated cellulose and Saran, which is a trade-name for polyvinylidine chloride. The tensile strength of some of said iibers approaches that of steel wire, while the density is about one fifth that of steel. The presn ent invention comprises means, apparatus, and structure whereby pressure vessels may be so constructed as to utilize the tensile strength of these organic iibers, oi which the above mentioned fibers are ymerely representative, but are preferred.

While these organic fibers with their high tensile strength relative to their Weight are capable of giving greater additional bursting strength to a vessel, with a resulting lower total weight than would be possible when using steel wire, the thermal coeillcient of expansion or contraction of these iibers is greater than that of steel and other metals. The present invention overcomes this disadvantage of high thermal coeiiicient of expansion of the fibers.

One object of this invention is to provide a light-weight container for fluids under pressure.

Another object is to provide a container for uids under pressure that will be light in weight as compared with all metal containers.

Another object is to provide a container for uids under pressure which is wound with organic fibers.

Another object is to utilize the strength of fibers having a higher coeicient of expansion than the pressure vessel around which they are wound as reinforcement.

Another object is to provide a container for iiuids under pressure comprising a center shell having a relatively low coeicient of expansion andan outer shell capable of expansion com mensurate with the expansion of a liquid between the two shells, the expansion of the outer shell under the influence of the expansion of the liquid being commensurate with the relatively high coeilicient of expansion of organic iibers wound around the outer shell.

Another object is to provide a simple, and useful, container for uids under pressure as shown and described, which will be economical in cost, and light in weight.

Numerous other objects and advantages will be apparent to those skilled in the art upon reading the accompanying specication, claims and drawings.

In the drawings- Figure l is an elevational view of a container embodying the present invention with parts broken away and in cross section to show details of construction.

Figure 2 is a cross sectional view of a portion oi Figure l taken along the line 2-2 looking in the direction indicated, with parts broken away to allow an enlarged view of said portion.

While an illustrative embodiment is shown in Figures l and 2 it should be understood that many other embodiments of the invention may be made within the scope of the present invention.

In Figure 1, there is shown an inner vessel 3 for containing a iiuid under superatmospheric pressure. Vessel 3 may be provided with a suitable means for ingress and egress of pressure fluid 4, comprising a valve housing 5, cut-off valve E having the usual hande l, and a connection 8 of any suitable type. If desired, any usual type of relief valve may be incorporated in house 5 with a passage communicating with fluid 4 for the relief of excessive pressure, but in order to simplify the disclosure such a relief valve is not shown.

Vessel 3 is preferably made of metal having relatively high bursting strength, such as steel, by any known method of making such vessels and valve housing 5 may be welded or brazed thereto.

-'Welding material in holes 9, or any known at- 3 taching means between 3 and 5 may be employed such as screw threads. In fact, 5 could be integral with 3 but such construction is not preferred.

The outer shell or vessel II is formed around vessel 3 by any known method of metal fabrication leaving a space therebetween for a suitable liquid I2. Both vessels 3 and I I may be made integral or in several parts suitably secured together by welding or pressed interlocking edges or other means old in the art, and vessel II is suitably secured to shell 3 by welding or other means at I3. In order to insert or remove liquid I2, a suitable filling valve I4 is preferably provided connected to shell II by suitable means I5. A simple plug could be used in place of valve I4, said plug being screw threaded or sealed to shell I I at I 5, but I prefer to employ a removable check valve I6 which will allow liquid I2 to enter vessel II, but will not allow its egress. When it is desired to remove liquid I2, the inner parts valve I4 can be unscrewed or otherwise removed from house I5 as a tire valve core is removed from its housing.

While not necessary in some applications of the invention, it is desirable in larger vessels to provide spacing means such as semielliptical springs I1 to aid in centering and supporting vessel 3 inside vessel II.

Vessel II 1s preferably made of thin metal and need not have very great strength. Vessel II is provided with a ribbed or corrugated construction, the corrugation being of the bellows type with straight sides (not shown) or preferably of the more or less sinuous corrugated construction shown in Figure 2 having depressed portions |8 and elevated portions I9. The rounded ends of vessel I I will of course be made strong enough to resist the pressure of liquid I2.

Around the exterior of shell II is to be wound a thread or series of threads or cables 2| composed of organic fibers. It is preferable to employ overlapping, sliding segments 22 made of any suitable material for transmitting pressure from elevated portions I9 of shell II to fibers 2|. Generally such segments 22 are preferably relatively thinner than shown in Figure 2 and may have their overlapping portions 23 tapered, if desired, in order to allow thread 2| to t snugly against a substantially cylindrical outer surface presented by segments 22 instead of having the thread 2| merely touch higher points I9 of shell II. Greater contact area between thread 2| and the surface of plates or segments 22 results in more equal distribution of force and there is less chance of failure oi' thread 2| because of concentrated stresses at any particular point.

Plates 22 may be made from any suitable organic or inorganic material but I prefer to use metal which may be secured by spots of solder or spot-welding to high points I9 at suitable intervals at points such as 2l. When nonmetallic substances are used glue or resins may be employed to fasten one or more points to shell II, at least temporarily for purposes of assembly. However plates 22 may be free from shell II and held in assembled relation by a jig until thread 2| is cemented in place and then will be held in place by the cement on thread 2 I.

Certain embodiments of my invention may eliminate plates 22, winding thread 2| directly on shell II with favorable results but such embodiments are not preferred.

Thread 2| may be wound on in one or more la. 'ers and may be composed of a single thread or cable of threads or a plurality of threads wound in series. I prefer to use a single strand for 2| and I prefer when using strands, threads or cables, to employ them with fibers oriented with the fiber length in the direction of length of the strand, thread or cable, that is longitudinally disposed in the thread or stand, in order to obtain the maximum tensile strength from the bers. For fibers in 2| I prefer Nylon. Rayon or Saran but those skilled in the art may easily select other suitable organic fibers which may be employed without departing from the scope of the present invention. Nylon has a high degree of orientation. While direct helical winding is preferred, a woven or knitted, felted or other fabric jacket may be employed in some instances in place of thread 2|.

While the ends of thread 2| may be secured by any suitable securing means to segments 22 or shell II, I prefer to overlap one or more turns of thread 2| and then paint the entire winding with any suitable glue, cement or resin such as a good spar varnish or a resin polymer such as Duco or the complete vessel may be dipped in gummed rubber which may be allowed to dry or which may be vulcanized. It should be easy for those skilled in the art to select suitable Blue, cement or resins compatible with the particular thread 2| employed, be it Nylon, Rayon," Saran" or other organic fibers, and by rubber I intend to include synthetic rubber. Preferably the coating material chosen should have elasticity compatible with the usual expansion of thread 2| under normal operating conditions.

Liquid I2 may be any suitable liquid having a coeiiicient of expansion commensurate with the coefficient of expansion of the organic fiber or ilbers selected for use as thread 2| I have found that hydrocarbon liquids, such as ether, butane, kerosene and other naphthas are generally preferable as liquid I2. Those skilled in the art can easily select a suitable fluid for I2 for the particular organic ber used in 2| and still remain within the scope of the present invention.

Operation.

Vessel 3 and its valve housing 5 is assembled and outer shell II is assembled around it. If plates 22 are employed, they are then at least temporarily positioned, or more or less secured to and around shell II; but if plates 22 are not employed thread 2| is then wound directly on shell I I. The winding of thread 2| on shell II, or in plates 22, may be made before or after liquid I2 is inserted between shells 3 and I I, but preferably before complete insertion. After thread 2| is wound on and secured to the vessel as described it may or may not be painted with a suitable coating material such as the glues, resins, cements and other materials described above.

Liquid I2 is filled in the space between 3 and II preferably Without any air bubbles or other gaseous inclusion in order to obtain the full effect of its coelcient of expansion.

The vessel is now filled with fluid under pressure through connection 8 and Valve 6 is closed.

Upon increase in temperature, thread 2| will expand to a greater degree than shell 3 but liquid I2 being a liquid of relatively high thermal coeflicient of expansion such as ether, butane,

kerosene, naphtha or the like, will expand at a rate commensurate with the expansion of thread 2| causing corrugations I8 and I9 of shell II to tend to straighten out and maintain pressure on threads 2|.

Thus, the pressure exerted by the compressed fluid 4 is transmitted through shell 3 and liquid |2 to the outer shell where it is off-set or neutralized by the tension of the fibers in the winding 2|. The liquid in the annular space and also the thickness of this annulus is so selected that the expansion or contraction with the change in temperature during normal transport and storage of the liquid I2 is such that a state of substantially constant tension is maintained, or at least the tension is maintained in a safe v range in the layer or layers of organic fibers windings 2|. The shell which contains the liquid annulus should be sufficiently expandable to allow it to expand and contract with change in temperature and thus maintain the hydrostatic pressure of the liquid |2 at a safe Value.

Besides securing thread 2|, the coating of glue or other materials suggested above has the additional function of preventing access of moisture or oxygen to thread 2| so that the organic fiber 2| will be preferably protected with a substantially air-tight, moisture-resistant coating.

Numerous changes may be made in the speclc embodiments of the invention described without departing from the spirit and substance of the invention, the scope of which is commensurate with the following claims.

Having described my invention I claim: l

l. A pressure vessel comprising in combination an inner shell adapted to receive fluids under superatmospheric pressure, an outer corrugated expansible shell, an elastic synthetic organic iiber reinforcement for said outer shell having a coeflicient of expansion substantially greater than thecoeilicient of expansion of said inner shell, and a liquid filling the space between said shells, said liquid having a coeilicient of expansion substantially commensurate with the coefficient of expansion of said organic ber reinforcement, whereby upon expansion and contraction due to normal temperature changes the tension on said vfiber reinforcement is maintained in a safe range.

2. The combination of claim 1 in which the elastic synthetic organic iiber reinforcement is a polyamide.

3. The combination of claim l in which the elastic synthetic organic fiber reinforcement is a regenerated cellulose.

4. The combination of claim l in which the elastic synthetic organic ber reinforcement is a polyvinylidine chloride.

5. The combination of claim l in which the liquid is a hydrocarbon.

6. A pressure vessel comprising in combination an inner shell adapted to receive fluids under superatmospheric pressure, an outer corrugated expansible shell, overlapping plates disposed around said outer shell and secured thereto, a liquid filling the space between said shells, a helical winding of an elastic thread of a synthetic organic fiber around said plates, means securing the end of said thread, and a coating of a suitable coating material covering said thread whereby said organic iiber is substantially protected from air and moisture.

7. A pressure vessel comprising in combination an inner shell adapted to receive fluids under superatmospheric pressure, an outer corrugated ex# pansible shell, overlapping plates disposed around said outer shell and secured thereto, a liquid lling the space between said shells, a. plurality of layers of helical winding of a continuous single strand of thread of a synthetic organic fiber around said plates, means securing the end of said thread, and a coating of a suitable coating material covering said thread whereby said organic fiber is substantially protected from air and moisture.

8. A pressure vessel comprising in combination an inner shell adapted to receive iiuids under superatmospheric pressure, an outer corrugated expansible shell, overlapping plates disposed around said outer shell, a liquid lling the space between said shells, a plurality of layers of helical winding of thread of a synthetic organic fiber around said plates, means securing the end of said thread, and a coating of a suitable coating material covering said thread whereby said organic ber is substantially protected from air and moisture.

9. A pressure vessel comprising in combination an inner shell adapted to receive iluids under superatmospheric pressure, an outer corrugated expansible shell, overlapping plates disposed around said outer shell and secured thereto, a liquid filling the space between said shells, a helical winding of synthetic organic fiber around said plates, and means securing the end of said thread.

l0. A pressure vessel comprising in combination an inner shell adapted to receive fluids under superatmospheric pressure, an outer corrugated expansible shell, overlapping plates disposed around said outer shell and secured thereto, a liquid filling the space between said shells, a winding of a thread of synthetic organic ber around said plates, means securing the end of said thread, and a coating of a suitable coating material covering said thread whereby said organic ber is substantially protected :from air and moisture.

11. A pressure vessel comprising in combination an inner shell adapted to receive fluids under superatmospheric pressure, an outer corrugated expansible shell, overlapping plates disposed around said outer shell, a liquid filling the space between said shells, a winding of synthetic organic ber around said plates, means securing the ends of said ber comprising a coating" of a suitable coating material covering said ends of said fiber and said liber whereby said organic ber as well as the ends is substantially protected from air and moisture.

l2. A pressure vessel comprising in combination an inner shell adapted to receive iluids under superatmospheric pressure, an outer corrugated expansible shell, overlapping plates disposed around said outer shell, a liquid filling the space between said shells, a winding of a thread of synthetic organic fiber around said plates which ber has a coefficient of expansion substantially commensurate with the coeicient oi expansion of said liquid, and means securing 'the end of said thread.

13. The combination of claim 12 in which the organic fiber reinforcement is a polyamide.

14. The combination of claim 12 in which the organic iiber reinforcement is a regenerated cellulose.

15. The combination of claim 12 in which the organic iiber reinforcement is a polyvinylidine chloride.

16. The combination of claim l2 in which the liquid is a hydrocarbon.

17. The invention oi' claim ll in which the coating material is a spar varnish.

18. The invention of claim ll in which the coating material is a resin polymer.

19. The invention of claim 11 in which the coating material is a rubber.

20. A pressure vessel comprising in combina'- tion an inner shell adapted to receive fluids under superatmospheric pressure, an outer corrugated shell, spacing means between said inner and outer shells, overlapping plates disposed around said outer shell, a plurality of layers of helical winding of elastic synthetic organic ber around said plates, means securing the end of said fiber, a coating of a suitable coating material covering said iiber whereby said fiber is substantially protected from air and moisture, and a liquid filling the space between said inner and outer shells.

2l. A pressure vessel comprising in combination an inner shell adapted to receive fluids under superatmospherlc pressure, an outer corrugated shell, spacing means between said inner and outer shells comprising semielliptical springs, overlapping plates disposed around said outer shell, a. plurality of layers of helical winding oi' elastic synthetic organic ber around said plates, means securing the end of said fiber, a coating ci' a suitable coating material covering said ber whereby said liber is substantially protected from air and moisture, and a liquid filling the space between said inner and outer shells.

FREDERICK E. FREY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 105,128 Roberts July 5, 1870 308,948 Bruce Dec. 9, 1884 1,651,521 Girardville Dec. 8, 1927 

